The eye the action receptor potential
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The Eye & The Action (Receptor) Potential. Packet #20 Chapter #49. Structure of the Eye. The Retina. Contains two types of photoreceptors Rods Black and white vision Cones Color vision

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The Eye & The Action (Receptor) Potential

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The eye the action receptor potential

The Eye & The Action (Receptor) Potential

Packet #20

Chapter #49


Structure of the eye

Structure of the Eye


The retina

The Retina

  • Contains two types of photoreceptors

    • Rods

      • Black and white vision

    • Cones

      • Color vision

  • These photoreceptors connect to a series of neurons that ultimately lead to the optic nerve which ultimately leads to the brain.


The structure of the rod

The Structure of the Rod

  • Contains disks that has the protein called rhodopsin within the disk’s membrane.

  • Rhodopsin

    • Contains two polypeptide chains called retinal and opsin.


Retinal

Retinal

  • Exists in two forms

    • Cis isomer

      • Exists when there is absence of light

    • Trans isomer

      • Exists when there is a presence of light


The production of a receptor potential in a rod cell

The Production of a Receptor Potential in a Rod Cell

  • Light isomerizes retinal, which activates rhodopsin.

    • What typeof enzyme would be used to make the change?

    • Retinal changes from the cisform to the trans form.

      • Ultimately causes rhodopsin to become active.


Production of a receptor potential i

Production of a Receptor Potential I

  • Light isomerizes retinal, which activate rhodopsin.


Production of a receptor potential ii

Production of a Receptor Potential II

  • Active rhodopsin in turn activate a G protein called transducin.


Production of a receptor potential iii

Production of a Receptor Potential III

  • Transducin activates the enzyme phodiesterase (PDE).


Production of a receptor potential iv

Production of a Receptor Potential IV

  • Activated PDE detaches cyclic guanosinemonophosphate (cGMP) from Na+ channels in the plasma membrane by hydrolyzing cGMP to GMP.


Production of a receptor potential iv1

Production of a Receptor Potential IV

  • The sodium channels close when cGMP detaches. The membrane’s permeability to Na+ decreases, and the rod hyperpolarizes.


The big picture

The Big Picture


Production of a receptor potential vi

Production of a Receptor Potential VI

  • The action potential moves along a series of nerve cells.

    • Horizontal

    • Bipolar

    • Amacrine

    • Ganglion cell

  • The message ultimately reaches the optic nerve fibers which lead to the brain.


Homework

Homework

  • Know how the eye focuses.

  • Know the cause of near and far sightedness.


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